This project will examine the neurobiological impact of early social deprivation rearing that can lead to an explosive violence syndrome in rhesus monkeys. In juvenile and adolescent monkeys, this syndrome is characterized by inappropriate, and often unsignalled, fierce attacks on other monkeys which are not mitigated by the victims age, gender, or size. The effects of differential rearing on neurotransmitter metabolism and social behavior will be determined throughout the study. To begin, measures of biogenic amine neurotransmitters and their metabolites in cerebrospinal fluid will be obtained from rhesus monkeys shortly after birth. Groups matched on these measures will be reared for the first 9 months of life in peer groups or in individual cages. Then the deprived monkeys will be housed in social groups of like-reared subjects. When they are first put into social groups, the socially deprived monkeys will have disrupted dominance and affiliative relationships and inordinately high levels of socially deprived monkeys will be behaviorally rehabilitated using established techniques of providing nurturing social contact with socially competent monkeys, i.e.," monkey therapists." After this treatment the behavior and neurochemical characteristics of the socially reared and socially deprived subjects will be similar on a day-to-day basis. Under this veneer will be differences in the neurobiological mechanisms that control aggression. Inordinate aggression will surface insocially deprived monkeys when they have to adapt to crowded housing conditions, introduction into new social groups, or to pharmacological challenges with d-amphetamine or alcohol. These challenges will reveal the underlying propensity for unregulated aggression and the inordinate neurochemical changes associated with outbursts. Effects of the challenges on CSF neurotransmitter measures will define a neurobiological syndrome underlying violent aggression that can be detected before aggressive outbursts, and show which subjects are at risk for this behavior. Definition of the pattern of changes may suggest further pharmacological or behavioral interventions that could limit or prevent violent outbursts.